Meredith Rawls' PhD Defense

Red Giants in Eclipsing Binaries as a Benchmark for AsteroseismologyMeredith L. Rawls Department of Astronomy New Mexico State University

April 8, 2016 • PhD Thesis Defense

@merrdiff

Image: G Perez, IAC, SMM

Meredith L. Rawls • @merrdiff

✦ Eclipsing binaries with light curves and radial velocities let us directly measure M, R

✦ Asteroseismology is a powerful tool to characterize lots of stars quickly, using light curves alone

✦ We can study oscillating stars in eclipsing binaries from two independent perspectives

✦ A set of well-characterized binaries lets us explore why some don’t oscillate when we think they should

How to measure stellar properties?

An asteroseismic revolution

Meredith L. Rawls • @merrdiff Figure: Huber et al. 2014

An asteroseismic revolution

Meredith L. Rawls • @merrdiff Figure: Huber et al. 2014


✦ Larger stars oscillate more slowly✦ Evolved giants: hours–days✦ Sun-like stars: minutes

Stochastic “ringing” oscillations in stars’ convective zones

100 μHz 1 mHz 500 Hz

Figure concept: P. Gaulme

Solar-like oscillations tell us about a star’s mean gravity and density


Δν

νmax

Power

Frequency ν

✦ Acoustic pressure modes✦ Buoyant gravity modes✦ Scaling relations


Chaplin & Miglio 2013

left side x-axis range

MS

MS

Subgiant

Subgiant

RGBbase

RGB

RGB

RGB

Redclump


✦ Kepler red giant catalog: ~14,000✦ Kepler eclipsing binary catalog: 2,500+✦ After cross-correlating: 19✦ Most systems are SB2, but 4 are SB1✦ Most are oscillators, but 4 are not

Searching for red giants in eclipsing binary systems

Gaulme et al. 2013, 2014


✦ Process light curves to “fill” eclipses and remove gaps

✦ Single set of oscillations✦ Broad and damped modes✦ Evolved onto the red clump

Characterizing a star: asteroseismology

70 80 90 100 110 120 130 140Frequency (µHz)

0

100

200

300

400

500

600

700

800

Smoothed

Pow

erDensity

(ppm

2µHz−

1)

0

100

200

300

400

500

600

700

800

KIC 9246715

Reference star

Rawls et al. 2016

KIC 9246715


Characterizing a star: binary modeling✦ Process Kepler light curve to

preserve eclipses✦ Extract radial velocities from

spectra via the broadening function✦ Get all velocities on one zeropoint✦ Suite of broadening function

programs in python:

github.com/mrawls/BF-rvplotter

Rawls et al. 2016

0.0

0.2

0.4 0.773 φ

2012-03-01

TRES 0.831 φ

2012-03-11

TRES 0.960 φ

2012-04-02

TRES 0.170 φ

2012-05-08

TRES

0.0

0.2

0.4 0.275 φ

2012-05-26

TRES 0.316 φ

2012-06-02

TRES 0.374 φ

2012-06-12

ARCES 0.460 φ

2012-06-27

ARCES

0.0

0.2

0.4 0.479 φ

2012-06-30

TRES 0.618 φ

2012-07-24

TRES 0.811 φ

2012-08-26

ARCES 0.812 φ

2012-08-26

ARCES

0.0

0.2

0.4 0.817 φ

2012-08-27

ARCES 0.864 φ

2012-09-04

ARCES 0.869 φ

2012-09-05

TRES 0.015 φ

2012-09-30

TRES

0.0

0.2

0.4 0.155 φ

2012-10-24

TRES 0.318 φ

2012-11-21

TRES 0.091 φ

2013-04-02

TRES

−60 −40 −20 0 20 40 60

0.196 φ

2013-04-20

ARCES

−60 −40 −20 0 20 40 60

0.0

0.2

0.4 0.511 φ

2013-06-13

ARCES

−60 −40 −20 0 20 40 60

0.982 φ

2013-09-02

ARCES

−60 −40 −20 0 20 40 60

0.023 φ

2013-09-09

ARCES

Smoothed BF

Two-Gaussian fit

Uncorrected Radial Velocity (km s−1)

BroadeningFu

nction

KIC 9246715


Characterizing a star: binary modeling

9.30

9.35

9.40

9.45

9.50

Magnitude

ELC Model

−60

−40

−20

0

20

40

RadialVelocity(km

s−1)

0.0 0.2 0.4 0.6 0.8 1.0

−0.0040.0000.004

−202

9.259.309.359.409.459.50M

agnitude

0.20 0.21 0.22 0.23

−0.0040.0000.004

0.49 0.50 0.51 0.52

Orbital Phase (conjunction at φ = 0.5)

Secondary Primary

∆

∆

∆

✦ Double red giant KIC 9246715✦ Stars are nearly twins; eclipse

depths vary due to geometry✦ Simultaneously fit radial

velocities and light curve✦ Minimize χ2 with 16 free

parameters using DE-MCMC optimizers

Rawls et al. 2016

Radialvelocities

Keplerlight curve

Eclipsezoom

KIC 9246715


Putting the pieces together KIC 9246715


Putting the pieces together KIC 9246715

2.15 M⊙, 8.30 R⊙ 2.17 M⊙, 8.37 R⊙


Putting the pieces together

200 400 600 800 1000 1200 140098.5

99

99.5

100

100.5

Time (BJD - 2454833)

∆I/I

(%)

?

KIC 9246715

Rawls et al. 2016

2.15 M⊙, 8.30 R⊙ 2.17 M⊙, 8.37 R⊙


✦ KIC 9246715 is in good company✦ Oscillation modes are damped or

missing in many red giant binaries✦ All modes affected equally✦ Compare properties of binaries with

strong, damped, and no oscillations✦ Determine what physical conditions

prevent resonant convection zones

Some other systems also show damped or absent oscillations

— no oscillations

νmax ~ 4 μHzνmax ~ 80 μHz

Gaulme et al. 2013


✦ Fourier decomposition turns dozens of composite spectra into one spectrum per star

✦ Stellar atmosphere modeling✦ Lines sensitive to magnetic fields✦ Suite of python programs to assist

with disentangling:

github.com/mrawls/FDBinary-tools

Disentangled spectra hold clues to magnetic activity

One of 23 high-res spectra (light from both stars)Star 1, Teff = 4990 ± 90 KStar 2, Teff = 5030 ± 80 K

KIC 9246715

http://github.com/mrawls/FDBinary-tools


✦ Magnetically sensitive Fe I lines don’t differ from non-sensitive ones

✦ Ca H & K lines too blue, noisy✦ Ca II λλ8498,8542 show no emission✦ Excess Hα absorption?✦ Orbital solution + light ratio both

needed for successful disentangling

Disentangled spectra hold clues to magnetic activity

5554 5557 5560−0.4−0.20.00.20.40.60.81.01.2 Fe i, mag

5572 5575 5578 5581

Fe i, non-mag

5686 5689 5692 5695

Fe i, non-mag

6298 6301 6304 6307

Fe i, mag

6559 6562 6565

Hα

6840 6844−0.4−0.20.00.20.40.60.81.01.2 Fe i, mag

7088 7092

Fe i, non-mag

Observed

Model

Difference

8490 8500 8510 8520 8530 8540 8550

Caii λλ8498,8542

Wavelength (A)

Scaled

Flux

5554 5557 5560−0.4−0.20.00.20.40.60.81.01.2 Fe i, mag

5572 5575 5578 5581

Fe i, non-mag

5686 5689 5692 5695

Fe i, non-mag

6298 6301 6304 6307

Fe i, mag

6559 6562 6565

Hα

6840 6844−0.4−0.20.00.20.40.60.81.01.2 Fe i, mag

7088 7092

Fe i, non-mag

Observed

Model

Difference

8500 8510 8520 8530 8540

Caii λλ8498,8542

Wavelength (A)

Scaled

Flux

Rawls et al. 2016

KIC 9246715


✦ Robotically-controlled 1m telescope at APO

✦ Kepler cannot measure color✦ Goal: compare eclipse fluxes

with out-of-eclipse flux✦ Especially useful for red

giants with faint companions

Multi-band photometry potentially constrains light ratio and temperatures


✦ Two non-oscillators✦ Mix of orbital periods (19 – 235 days)✦ Three with variability > 1%✦ Two with phase effects✦ Mix of eccentricities (< 0.001 – 0.38)✦ Observed the most in 1m campaign

Choosing a representative subset of red giant binaries


Modeling red giants with faint companions

279.764 279.766 279.768

10000

30000

50000

T0 conj

−0.15652 −0.15648 −0.15644

5000

15000

25000

e cosω

0.1650 0.1660 0.1670

10000

30000

50000

e sinω

89.0 89.4

10000

30000

50000

i

1.12 1.16 1.20

5000

15000

25000

M1

5800 6200 6600

20000

60000

100000 Teff, 1

0.73 0.75 0.77

5000

15000

25000

T2/T1

0.0086 0.0088 0.0090

5000

15000

25000

R1/a

0.0688 0.0692 0.0696

5000

15000

25000

R2/a

25.5 26.5

5000

15000

25000

K1

0.05 0.15 0.25

5000

15000

25000 LD1 q1

0.56 0.60 0.64

10000

30000

50000 LD1 q2

0.4 0.6 0.8

10000

30000

50000

LD2 q1

0.35 0.45 0.55

10000

30000

50000

LD2 q2

0.01 0.03 0.05

20000

60000

100000

Kepler contam

207.1076 207.1080 207.1084

5000

15000

25000

Period

KIC 3955867Broadeningfunction fits

KIC 10001167Disentangledgiant spectrum

KIC 7037405ELC fit parameterdistributions


KIC 8702921

P = 19.4 dayse = 0.10variability ~ 1.4%

No Ca II emissionDeep Hα line

The only SB1in the sample

0.27 M⊙

0.29 R⊙

1.67 M⊙

5.32 R⊙1/7


KIC 92916291.11 M⊙

1.83 R⊙

1.13 M⊙

7.93 R⊙

P = 20.7 dayse = 0.0006variability ~ 16%

Ca II net emissionNormal Hα line

Fast rotatorBVRI used in fit

2/7


KIC 39558670.92 M⊙

0.97 R⊙

1.10 M⊙

8.24 R⊙

P = 33.7 dayse = 0.01variability ~ 23%

Ca II net emissionHα not too deep

Fast rotator

3/7


KIC 100011670.81 M⊙

0.97 R⊙

0.86 M⊙

12.73 R⊙



Phase effects

4/7


KIC 57861541.02 M⊙

1.56 R⊙

1.06 M⊙

11.01 R⊙



Most eccentric

5/7


KIC 70374051.15 M⊙

1.74 R⊙

1.27 M⊙

13.72 R⊙



25 APOGEE RVsMcKeever+ in prep

6/7


KIC 99703961.00 M⊙

1.08 R⊙

1.17 M⊙

7.70 R⊙



Kepler LC gapsBVRI used in fit

7/7


✦ Seismic M, R are both too large✦ Densities and gravities nearly agree✦ Stars least like the Sun differ the most✦ Spectroscopic gravities are too high

The scaling relations are not perfect

Coming soon: Gaulme et al. 2016

Mass Radius

Density(Δν)

Gravity(νmax)


✦ The most active giants lack oscillations, have short periods, and are rotationally synchronous

✦ They also show differential rotation✦ Ca II net emission agrees with

strongest photometric variability✦ Hα may trace chromospheric activity

Magnetic activity roundup

Robinson et al. 1990


10 100 30010

100

2005866138

9246715

7377422

4473933

10015516

8430105

8435232

5179609

4569590530877871332863955867

6307537

5193386

929162911235323

8702921

7943602

Porb [days]

Pvar[d

ays]

5 : 14 : 1 3 : 1 2 : 1 1 : 1 12: 1 Evidence for orbital &

rotational resonances

More stellar variability

Less stellar variability

Stronger oscillationsWeaker oscillations

Gaulme et al. 2014and Ravenel et al. in prep

✦ Binaries with no oscillations more likely to be synchronized

✦ Binaries with synchronization more likely to be active (variable)


✦ MESA: 1D stellar profiles over time✦ Initialize model with M & metallicity;

let star evolve to present R✦ KIC 9246715 contains the only red

clump stars in this sample✦ Adjusted mixing-length parameter

(increase efficiency of convection) to get sufficiently small RC stars

Stellar evolution models constrain tidal history and age KIC 9246715


✦ Depends on stellar evolution and influence of companion star

✦Δe is a function of M, M2/M, Porb, I(t)✦ I(t) is a function of Teff(t), Menv(t), R(t)

Tidal forces over time

Verbunt & Phinney 1995

KIC 9246715


✦ Depends on stellar evolution and influence of companion star

✦Δe is a function of M, M2/M, Porb, I(t)✦ I(t) is a function of Teff(t), Menv(t), R(t)

Tidal forces over time

Verbunt & Phinney 1995

M2/M = 0.989KIC 9291629


✦ Rotation synchronization should happen before orbit circularization

✦ Two most active giants with short periods are nearly circularized

✦ Eccentric systems have not had enough time for tides to circularize

✦ Two outliers/in-between cases

Predicted changes in eccentricity

Prediction: a range of oscillation populations


Tidally-induced“heartbeat” pulsations

No solar-likeoscillations

Damped solar-like oscillations

Oscillates likea single star

8702921

9291629

395586710001167

57861549246715

7037405

9970396


✦ Distances computed via theoretical bolometric corrections, updated KIC extinctions, & JHK magnitudes from 2MASS

✦ No clear galactic [Fe/H] gradient

Galactic context

Southworth et al. 2005


Pipeline comparisons

temperature

surfacegravity

metallicity

distance


✦ Solar-like oscillations are damped by magnetism & tides, which often occur together

✦ Most pronounced for short-period, spotty, synchronized and circularized systems

✦ The asteroseismic scaling relations are least accurate for stars least like the Sun

✦ Scaling relations overestimate giant M, R✦ These stars are references for survey pipelines✦ Asteroseismic surveys will tend to miss active

stars and close binaries

Red giant binaries are powerful benchmarks for asteroseismology

Science

Meredith Rawls' PhD Defense